GWP stands for Global Warming Potential, and in HVAC it refers to how much heat a refrigerant traps in the atmosphere compared to carbon dioxide. CO2 has a GWP of 1, so a refrigerant with a GWP of 1,430 traps 1,430 times more heat than the same amount of CO2 over 100 years. This number has become one of the most important specs in the HVAC industry because new regulations are forcing a rapid shift away from high-GWP refrigerants.
How GWP Is Calculated
GWP measures how much energy one ton of a gas absorbs over a set time period, relative to one ton of carbon dioxide. The standard timeframe is 100 years, established by the Intergovernmental Panel on Climate Change. CO2 always has a GWP of 1 because it’s the baseline everything else is compared against.
The number reflects two things: how effectively the gas absorbs infrared radiation (heat), and how long it lingers in the atmosphere before breaking down. A refrigerant can have a high GWP either because it’s extremely good at trapping heat, because it persists for decades, or both. R-410A, the refrigerant that has dominated residential air conditioning for the past 20 years, has a GWP of 2,088. That means every pound that leaks from your system traps as much heat as 2,088 pounds of CO2 would over a century.
GWP vs. Ozone Depletion Potential
If you’ve heard of the ozone layer problem, you might wonder how GWP relates. They measure completely different things. Ozone Depletion Potential (ODP) measures how much a chemical damages the ozone layer. GWP measures how much it contributes to global warming. A refrigerant can score high on one and low on the other.
This distinction matters because of history. The older refrigerant R-22 (commonly called Freon) was phased out because it destroyed the ozone layer. The HFC refrigerants that replaced it, like R-410A and R-134a, solved the ozone problem completely. But they turned out to be incredibly potent greenhouse gases. R-134a, the most common refrigerant in car air conditioning since the 1990s, has a GWP of 1,430. CFC-12, the refrigerant it replaced, had a GWP of 10,900 and also depleted ozone. The industry essentially traded one environmental problem for a smaller but still serious one.
GWP Values for Common Refrigerants
The range of GWP values across HVAC refrigerants is enormous. Here’s how the most relevant ones compare:
- R-22 (Freon): GWP of 1,810. Phased out due to ozone depletion. Still exists in older systems but can no longer be manufactured or imported in new equipment.
- R-410A: GWP of 2,088. The current standard in most residential AC and heat pump systems. Being phased down under new regulations.
- R-32: GWP of 675. Already common in parts of Asia and Europe. About one-third the GWP of R-410A.
- R-454B: GWP of approximately 466. The leading replacement for R-410A in U.S. residential systems. Marketed under brand names like Opteon XL41.
- R-134a: GWP of 1,430. Widely used in automotive AC and some commercial chillers.
- HFO-1234yf: GWP of 4. Already replacing R-134a in new cars.
- R-290 (propane): GWP of approximately 3. Used in some small commercial refrigeration and increasingly in window AC units.
- R-744 (CO2): GWP of 1. Used in commercial refrigeration, especially supermarkets.
- R-717 (ammonia): GWP of 0. Used in large industrial and commercial refrigeration.
Natural refrigerants like propane, CO2, and ammonia have zero or near-zero GWP and are considered future-proof from a regulatory standpoint. Their challenge is safety: propane is flammable, ammonia is toxic, and CO2 operates at very high pressures. Each requires specific equipment design to manage those risks.
Why GWP Matters Now: The Regulations
The AIM Act, signed into U.S. law in 2020, requires an 85 percent reduction in HFC production and consumption from historic baseline levels by 2036. The phasedown follows a stepped schedule:
- 2020 to 2023: 90 percent of baseline allowed
- 2024 to 2028: 60 percent of baseline
- 2029 to 2033: 30 percent of baseline
- 2034 to 2035: 20 percent of baseline
- 2036 and beyond: 15 percent of baseline
This isn’t just about manufacturing caps. Starting January 1, 2025, restrictions took effect on the use of higher-GWP HFCs in new refrigeration, air conditioning, and heat pump equipment. For residential AC split systems specifically, any whole new system installed after January 1, 2026, must use a lower-GWP refrigerant. That effectively means new residential systems will run on refrigerants like R-454B instead of R-410A.
Internationally, the Kigali Amendment to the Montreal Protocol sets a similar trajectory. Developed countries began their first reduction step in 2019 and will complete the phasedown by 2036. Most developing countries started reducing in 2024 and have until 2045.
For cars, the timeline moved even faster. As of model year 2025, new light-duty passenger vehicles manufactured or imported into the U.S. cannot use a refrigerant with a GWP of 150 or greater. That’s why most new cars already use HFO-1234yf (GWP of 4) instead of R-134a.
What A2L Safety Ratings Mean
Most of the lower-GWP refrigerants replacing R-410A carry an ASHRAE safety classification of A2L. This tells you two things. The “A” means lower toxicity, and the “2L” means mildly flammable with a very slow burning velocity. R-410A, by contrast, is classified A1, meaning it doesn’t propagate a flame at all.
The shift to A2L refrigerants has required updates to building codes, equipment design, and installation practices. HVAC systems using A2L refrigerants include leak detection sensors and are designed to limit charge sizes. For homeowners, the practical difference is minimal. You won’t need to do anything special to live with an A2L system, but your technician will follow updated safety protocols during installation and service.
What This Means If You’re Buying or Replacing Equipment
If your current AC or heat pump uses R-410A, it will continue to work and can still be serviced with R-410A refrigerant for the foreseeable future. The regulations target new equipment manufacturing, not existing installations. However, as production caps tighten through 2036, R-410A will likely become more expensive over time, following the same pattern R-22 did after its phasedown began.
If you’re buying a new system after January 2026, it will almost certainly use a lower-GWP refrigerant like R-454B. Equipment using these newer refrigerants may cost slightly more initially due to updated components and safety features, but the refrigerants themselves tend to be more energy-efficient. Research from the California Energy Commission found that systems using R-290 (propane) could save an estimated $44.50 per ton of CO2 equivalent due to lower operating costs from higher energy efficiency. Similar efficiency gains are expected with other low-GWP options.
The bottom line: GWP is the number that determines which refrigerants stay on the market and which get phased out. It directly shapes what equipment is available to you, what it costs to operate, and what refrigerant your technician charges into it. If you’re making an HVAC decision in the next few years, understanding GWP helps you make sense of why the options are changing and which direction the industry is heading.